1. Field of the Invention
This invention relates to the field of hand-held power tools, and more specifically to a hand-held power tool suitable for sanding or rasping applications.
2. Description of the Prior Art
Woodworking as a hobby has become quite popular. Tools which were once marketed only to professional woodworkers are now conveniently available to woodworkers of all skills, from beginners to seasoned hobbyists and professionals. Hand-held power tools come in a number of different varieties suitable for professional and hobbyist applications. For instance, woodworkers are quite familiar with hand-held power tools such as drills, circular saws, plate joiners, sanders, routers, planers, etc. But due to design constraints, certain tools have been limited to bench top applications. One of these is the oscillating spindle sander.
An oscillating spindle sander is a tool which, as its name implies, may be used to sand a workpiece. A spindle typically protrudes from the bench top. The spindle is operatively connected to a motor which, through a series of belts, pulleys, gears or other transmission devices, causes the spindle to rotate. A drum is typically secured to the spindle. Sandpaper or other roughened material is applied to the drum. The rotating drum, along with the sandpaper, is brought into contact with the workpiece for sanding or removing material from the edge of the workpiece. The spindle is also caused to reciprocate in an axial direction. Otherwise, the same segment of the sandpaper would be repeatedly applied to the workpiece. This would cause premature wearing of the sandpaper, as well as the generation of excessive heat and burning of the workpiece.
To date, no commercial hand-held oscillating spindle sanders are available on the market. Instead, all of the oscillating spindle sanders are of the bench top variety. Among other reasons, one of the challenges facing a designer of a hand-held oscillating spindle sander is developing a light-weight, compact design which permits hand-held operation. Until now, no such tool had been designed to satisfy these competing criteria. Solutions have been proposed. None have been commercially viable on a large scale.
For example, U.S. Pat. Nos. 5,678,292 and 5,957,765 to Kimbel et al. disclose a hand-held machine tool which may be used for sanding a workpiece. Oscillation of the sanding tool is provided by one of several proposed oscillation devices, ranging from a swash plate to a driving disk associated with a rotating gear which is adapted to engage a disk follower member on the output shaft. In all but one of these embodiments, the drive shaft is perpendicular to the output shaft. Bevel gears are therefore needed to turn the direction of rotational power from perpendicular to parallel with respect to the drive shaft. This leads to a decrease in power efficiency compared to the configuration where the drive shaft and output shaft are parallel with one another.
Using a swash plate to create the oscillation of the output shaft unnecessarily complicates the tool. The swash plate is attached at an angle to a so-called intermediate shaft. As a consequence, the swash plate and the intermediate shaft are spaced from and parallel to the output shaft. A grooved roller is operatively coupled to the output shaft and engages the swash plate. As the swash plate rotates, the grooved roller is pulled up and down in a direction corresponding to the axis of the output shaft. This causes the output shaft to oscillate.
In an alternative embodiment where the swash plate is integrated into the output shaft, the grooved roller is replaced with a pin member which slides along the surface of the swash plate. This undesirable configuration could lead to the premature wearing of either the swash plate, the pin, or both. Further, this configuration would inevitably be relatively noisy in operation since the pin slides, rather than rolls, along the surface of the swash plate.
In all of the embodiments, the swash plate is relatively thin. The swash plate is cantilevered on the intermediate shaft. In operation of the tool, the swash plate would be subjected to significant forces resulting from the reciprocation of the grooved roller or pin member contacting the swash plate. Consequently, the swash plate arrangement is not the most effective mechanism for creating the oscillation motion of the output shaft.
The sander of the foregoing patents suffers from several other drawbacks. It does not have variable speed operation. Different wood stock has different surface hardness. Without a variable speed capability, the sander could damage softer wood or take longer to sand harder wood. Also, the sander of the foregoing patents does not include an edge guide assembly for precision sanding of straight surfaces. It also does not provide for means to attach the sander to the underside of a work table for conversion to a bench top oscillating spindle sander.
For these and other reasons, tools such as that disclosed in the foregoing patents have not been commercialized on a large scale. Professional woodworkers and hobbyists thus have been limited to bench top oscillating spindle sander applications. But, bench top applications limit the ability of the woodworker to truly enjoy the benefits of the oscillating spindle sander. With a bench top oscillating spindle sander, the workpiece must be moved relative to the sander during the sanding operation rather than moving the sander relative to the workpiece. Consequently, the oscillating spindle sanders of the bench top variety cannot be used to sand a workpiece which is not movable due to its size, weight, or installation constraints. For example, a bench top oscillating spindle sander cannot easily be used to sand solid surface sink cutouts on installed countertops, or the finished edges of an installed hardwood stair tread. Further, the oscillating spindle sanders of the bench top variety require a fair amount of dedicated shop space.
These and other disadvantages of the oscillating spindle sanders of the prior art are overcome by the invention of the preferred embodiments.
It is an object of the preferred embodiments to provide a portable, hand-held oscillating spindle sander.
It is a further object of the preferred embodiments to provide an oscillating spindle sander which has an integral dust collection system.
It is a further object of the preferred embodiments to provide an oscillating spindle sander in which the power transmission, including the oscillation, is achieved by a unique combination of elements which provide a compact construction.
It is a further object of the preferred embodiments to provide an oscillating spindle sander including a removable and adjustable edge guide assembly.
It is a further object of the preferred embodiments to provide an oscillating spindle sander having variable speed operation.
It is a further object of the preferred embodiments to provide an oscillating spindle sander which has internal support structures configured for easy assembly.
It is a further object of the preferred embodiments to provide an oscillating spindle sander which has adequate means for cooling the internal moving components of the sander.
It is a further object of the preferred embodiments to provide an oscillating spindle sander which has a thumb rest formed on the base for allowing a user to rest a thumb on the base while sanding.
It is a further object of the preferred embodiments to provide an oscillating spindle sander which has means for mounting the sander to the underside of a work table for conversion to a bench top oscillating spindle sander.
It is a further object of the preferred embodiments to provide an oscillating spindle sander which has a favorable ratio of oscillation to rotation of the sanding spindle.
These and other features, objects and advantages are achieved by a portable, hand-held oscillating spindle sander comprising a housing, a base associated with the housing for contacting the workpiece, a motor at least partially contained within the housing, an output shaft extending from the housing and adapted to drive a sanding tool. The output shaft is operatively coupled to the motor through a transmission so that the rotational power of the motor is transmitted to the output shaft. An oscillation device is associated with the output shaft comprising first and second camming surfaces associated with the output shaft for relative rotation with respect to the output shaft. A cam follower is operatively coupled to the output shaft for rotation with the output shaft, the cam follower engaging the first and second camming surfaces so that upon rotation of the output shaft, the cam follower moves along the camming surface to cause the output shaft to have an oscillatory translational component of movement.
The portable, hand-held oscillating spindle sander of the preferred embodiments advantageously incorporates a dust collection mechanism. Namely, the dust collection mechanism is integrated with the base assembly. The base assembly is formed with an opening through which the output shaft protrudes. A toroidal cavity extends around the opening. A plurality of vacuum ports communicate with the opening. The vacuum created within the toroidal cavity causes the dust created during sanding to be sucked within the toroidal cavity. From there, the dust is disposed through a hose, which is adapted to be attached to the front of the base.
The portable, hand-held oscillating spindle sander according to the preferred embodiments advantageously is provided with a variable speed mechanism. Namely, a variable speed dial switch permits the tool to be operated between a minimum of about 2400 rpm to a maximum of about 3600 rpm. This variability in the speed of the tool advantageously permits the shopsmith to adjust for the characteristics of the workpiece to be sanded.
The portable, hand-held oscillating spindle sander of the preferred embodiments is further advantageously constructed with internal component supporting structures. This provides ease in assembly. Namely, other than the outer, clam-shell casing, the entire supporting apparatus for the working components for the oscillating spindle sander are provided by two opposed structures, an internal support structure and a bearing housing. The internal support structure includes a plurality of annular recesses adapted to receive the bearings on which the rotating shafts are mounted. At their other ends, the rotating shafts are received in bearings mounted in annular recesses in the bearing housing. The internal support structure and the bearing housing are conveniently attached to one another after the motor, transmission means, and oscillation means are positioned for assembly. Consequently, the operational parts of the oscillating spindle sander are conveniently manufactured as an integrated unit.
The portable, hand-held oscillating spindle sander further includes an edge guide assembly. The edge guide assembly is adapted to be attached to the bottom of the base. The edge guide assembly preferably includes an adjustable infeed and an adjustable outfeed. Namely, the infeed and outfeed of the edge guide may slide along a rail formed on respective sides of the edge guide body. The adjustable edge guides assist the shopsmith in removing the precise amount of stock from the workpiece.
The portable, hand-held oscillating spindle sander further includes a thumb rest formed on the base for allowing a user to place a thumb of one hand on the thumb rest of the base and using the other fingers of that hand to feel the workpiece and determine if the sander is flat against the workpiece.
The portable, hand-held oscillating spindle sander further includes means for mounting the sander to the underside of a work table for converting the hand-held sander into a bench top sander.
The portable, hand-held oscillating spindle sander further includes a cooling fan and vents for directing cooling air around the internal moving components of the sander for cooling purposes.
The portable, hand-held oscillating spindle sander further includes a transmission that permits the output shaft to oscillate at a favorable ratio to its rotational speed.
The portable, hand-held oscillating spindle sander further includes increased friction means on the sanding spindle to prevent relative rotation between the sanding spindle and a sanding sleeve mounted on the sanding spindle.
Further objects, features and advantages of the oscillating spindle sander according to the preferred embodiments will become evident when the detailed description of the preferred embodiments is read in conjunction with the drawing figures appended hereto.